Users of multimedia products get more demanding on high-quality audio service, and a lossless audio coding technique has been standardized as MPEG-4 ALS for accommodating the demand of the market.
MPEG-4 ALS consists of two main parts such as forward linear prediction and entropy coding.
In forward linear prediction, the optimal predictor coefficients are usually estimated for each block by the autocorrelation method.
The autocorrelation method may use the Levinson-Durbin algorithm. The autocorrelation method has additionally the advantage of providing a simple means that iteratively adapts the order of the predictor. Such Linear Prediction Coefficients (LPCs) are used for short-term predictors, and generally implemented with an FIR filter.
However, MPEG-4 ALS supports the LPCs order up to 1023 with the bit resolution of 32-bit Pulse Code Modulation (PCM), and the wide range of the filter order highly increases the complexity of short-term predictors. Particularly, the short-term predictors are most complicated in implementing the MPEG-4 ALS encoder.
The processing time of short-term predictors depends on the calculation time of linear prediction filter coefficients, and various architectures have been proposed in order to provide high-speed and area-efficient implementations for the FIR filter based short-term predictor.
However, such architectures do not consider the timing problem and area efficiency in pipeline scheme that have not been perfectly matched in coefficient calculation time of MPEG-4 ALS.